The ground may be cleared here by saying what our problems are not. There is no question as to whether Lamarckism or Darwinism represents the predominant partner in the story of life; there is no question of the “relative importance of natural selection and the Lamarckian factors in organic evolution,” though such a question may arise when once Lamarckism has received its passport from the authorities; but the time is not yet. Nor is it a question as to the reason why adaptive modifications are so constantly present in the germ. It is not a question of Nature _or_ Nurture, but perhaps may be found to be a study of Nature _and_ Nurture. It is not a question of Mendelian analysis, nor as to the distribution of either mutations on the one hand, nor of minute fluctuating variations on the other. The problems are therefore limited in scope and ambition, and are none the worse for that, as being better open to correction or support. The Problems Considered. It seems but natural to most persons who contemplate with any care the ever-changing and progressive drama of life in plants and animals that unquestionably the _dramatis personæ_ by their individual response to the environments and exercise of their functions must contribute a share, however small, to their offspring. When first this view presents itself to their minds they resent as “unnatural” any other possibility. But, alas! they find that such a conclusion is not permitted in those regions where alone the white light of science shines. Here the writ of _a priori_ does not run. The spirit of inquiry makes its challenge to every presupposition and every assertion in its province--even those of current science. I have shown that this particular assumption of the natural man was firmly challenged by Weismann, who was not the first, but the greatest, biologist to teach that modifications are not transmitted. Accordingly, agreeable and convenient as it would be to assume the Lamarckian hypothesis as a working one, it needs in the present day to be supported by evidence before this can be allowed. Facts, then, against Weismann’s dogma are demanded and of such a kind as will satisfy so powerful an advocate of his own views. In passing it may be remarked again that there is nothing so misleading as facts, except statistics, and for both sides to bear in mind the warning of a French writer that in such inquiries as this we should be careful lest we find the facts for which we are looking.